EP2216352A1 - 2K polyurethane coating for carrier films - Google Patents

Abstract

Aqueous two-component polyurethane lacquer comprises: (a) at least a hydroxy-functional polyester polyurethane dispersion comprising, as structural components, (a1) hydroxy-functional polyester, (a2) linear, hydroxy functional polycarbonates, (a3) at least one ionic or potentially ionic compound with at least an acid group and at least an isocyanate reactive group, (a4) at least one (cyclo)aliphatic diisocyanate, and (a5) low molecular weight hydroxy- and/or amino functional compounds; and (b) at least a polyisocyanate crosslinker. Aqueous two-component polyurethane lacquer comprises: (a) at least a hydroxy-functional polyester polyurethane dispersion comprising, as structural components, (a1) hydroxy-functional polyester, (a2) linear, hydroxy functional polycarbonates, (a3) at least one ionic or potentially ionic compound with at least an acid group and at least an isocyanate reactive group, (a4) at least one (cyclo)aliphatic diisocyanate, and (a5) low molecular weight hydroxy- and/or amino functional compounds; and (b) at least a polyisocyanate crosslinker, where the crosslinking ratio of isocyanate groups of (b) and hydroxy groups of (a) is 1:1-1.6:1.

Description

The invention relates to a two-component (2K) -polyurethane paint for a carrier film, a process for its preparation and their use for the equipment of plastic moldings.

The surface of many thermoplastics is relatively sensitive to their mechanical and chemical resistance. The direct coloring by coloring the substrate is limited in terms of the colors and effects to be achieved. In addition, injection molding may cause visible surface defects, such as flow lines, that are unacceptable for vision applications.

In addition, foamed components frequently have surface defects and / or pores, which considerably complicate error-free painting. Especially after any grinding operations, the affected parts must be manually filled prior to painting.

The coating of plastic moldings to achieve the required resistance properties and the desired visual appearance is well known. In the field of high-quality plastic parts with corresponding requirements in terms of mechanics, durability and longevity, coatings based on polyurethane dominate, which represent a compromise between a mechanism adapted to the flexible substrates and the required resistance properties.

Composite elements of lacquer layer and plastic component are usually produced by subsequent painting in the spraying or dipping process of the previously foamed or produced by injection molding component. In automotive engineering in particular, this is the preferred procedure for producing large-area components or those with complex geometry. This subsequent application of the lacquer layer requires a large number of separate working steps, some of which have to be carried out manually and can not be automated. In addition, certain partial surfaces of the component can be coated only very expensive. When painting three-dimensional body is also to be expected with a significant loss of material of the paint, the so-called overspray. In addition, the error rate in the painting of three-dimensional parts is significantly higher than in the technically easier coating of two-dimensional films.

In order to arrive at an efficient, resource-saving and cost-effective process, methods are known in which initially plastic films are coated over a large area by means of common coating methods such as doctoring, rolling or spraying and this coating by physical drying or partial curing dries almost tack-free. These films can then be deformed at elevated temperatures and then glued, back-injected or backfoamed. This concept offers a great deal of potential for the production of, for example, components by plastic processors, whereby the more complex painting step of three-dimensional components can be replaced by the simpler coating of a flat substrate.

EP-A 1 647 399 describes composite moldings consisting of a carrier film and applied to this film soft-touch lacquer. This carrier foil is used for injection-molding or back-pressing with thermoplastics without damaging the soft-touch lacquer layer. For example, there are no shiny spots and no cracks in the paint layer. The polyol component contained in the paint formulation contains, in addition to building blocks which react chemically with the polyisocyanate crosslinker, elastifying, hydroxyl- and / or amine-group-free polyurethanes. These dry only physically and do not crosslink by a chemical reaction on the substrate. Therefore, such coatings do not achieve the high level of scratch and chemical resistance of fully chemically reacting paints.

As a rule, good surface properties require a high crosslinking density of the coating. A disadvantage of high crosslinking densities, however, is that they lead to duromeric behavior with maximum possible degrees of stretching of only a few percent, so that the coating tends to crack during the deformation process.

In addition, for an economical use of this method, the intermediate winding of the coated, deformable film on rolls is necessary. The pressure and temperature stresses which occur in the rolls place special demands on the blocking resistance of the coating. Block resistance means the bonding effect that occurs when joining two coated surfaces under loads such as temperature or pressure. This apparent conflict between the required high crosslink density and the desired high degree of stretching can be solved, for example, by performing the drying / curing of the coating in two steps, before and after the deformation. Particularly suitable for post-curing is a radiation-induced crosslinking reaction in the coating.

In the WO-A 2005/099943 is a flexible laminate with a support and at least one applied to the support layer of a curable lacquer, wherein the paint contains a double bond-containing binder having a glass transition temperature Tg between -15 ° C to 20 ° C, which is not tacky after thermal drying. In the WO-A 2005/099943 is further described that the coating may be prone to dust due to the low Tg.

In the example, a degree of drying / blocking resistance of the coating is achieved before the radiation curing, in which after a load of 500 g / cm ² for 60 s at 10 ° C still embossings of a filter paper are visible. The stresses on a coating in a film roll are usually higher in terms of pressure and temperature. The possibility of winding the films on rollers before the radiation curing of the paint is therefore not described in this document. Disadvantage of this method is also the need for a radiation treatment of the three-dimensional finished parts in order to achieve the desired resistance properties. The curing of the paint in so-called shadow regions of the component is thus not always guaranteed safe.

The object of the present invention was therefore to provide a novel aqueous polyurethane lacquer for coating a carrier film, which has a high level of scratch and chemical resistance with simultaneously high degrees of stretching. In addition, the coated carrier film should be able to be wound on rolls without the coating showing cracks. It should also be given a high blocking resistance, i. that the carrier film should be able to unwind easily without sticking from the roll.

It has now been found that special aqueous polyurethane coatings as a coating on thermoplastic carrier films solve this problem.

1. A) mindestens eine hydroxyfunktionelle Polyesterpolyurethan-Dispersion, enthaltend als Aufbaukomponenten
   • a1) lineare oder verzweigte, hydroxyfunktionelle Polyester,
   • a2) lineare, hydroxyfunktionelle Polycarbonate,
   • a3) mindestens eine ionische oder potentiell ionische Verbindung mit mindestens einer Säuregruppe und mindestens einer gegenüber Isocyanatgruppen reaktionsfähigen Gruppe,
   • a4) mindestens ein (cyclo)aliphatischen Diisocyanat sowie
   • a5) niedermolekulare hydroxy- und/ oder aminofunktionelle Verbindungen.
     sowie
2. B) mindestens einen Polyisocyanat-Vernetzer, dadurch gekennzeichnet, dass
   das Vernetzungsverhältnis aus Isocyanat-Gruppen aus B) und Hydroxy-Gruppen aus A) zwischen 1,0:1 und 1,6 : 1 liegt. Bevorzugt beträgt das Vernetzungsverhältnis 1,2:1 bis 1,4 :1.

The present invention thus provides an aqueous 2-component polyurethane lacquer containing

1. A) at least one hydroxy-functional polyester polyurethane dispersion containing as structural components
   • a1) linear or branched, hydroxy-functional polyesters,
   • a2) linear, hydroxy-functional polycarbonates,
   • a3) at least one ionic or potentially ionic compound having at least one acid group and at least one isocyanate-reactive group,
   • a4) at least one (cyclo) aliphatic diisocyanate and
   • a5) low molecular weight hydroxy and / or amino functional compounds.
     such as
2. B) at least one polyisocyanate crosslinker, characterized in that
   the crosslinking ratio of isocyanate groups from B) and hydroxy groups from A) is between 1.0: 1 and 1.6: 1. The crosslinking ratio is preferably 1.2: 1 to 1.4: 1.

Optionally, the 2K polyurethane paint may contain other auxiliaries and additives C).

The average functionality of the polyisocyanates B) is 2.5 to 3.3, preferably 2.8 to 3.0.

The preparation of the polyester polyurethane dispersion A) is effected by polyaddition of the components a1) to a5) and subsequent neutralization of the carboxylic acid and dispersion in water.

The components a5) are preferably low molecular weight compounds of molecular weight Mn 62 to 400 g / mol which have a total of two or more, preferably three hydroxyl and / or amino groups.

Preferred polyester-polyurethane dispersions A) contain 20 to 50% by weight, preferably 30 to 40% by weight of component a1), 20 to 50% by weight, preferably 30 to 40% by weight of component a2), 2 to 6 Wt .-%, preferably 3 to 5 wt .-% of component a3), 10 to 30 wt .-%, preferably 15 to 25 wt .-% of component a4), 0.5 to 10 wt .-%, preferably 2 to 5 wt .-% component a5), wherein the percentages a1) to a5) to 100 wt .-% complement.

The acid groups incorporated to stabilize the dispersion via component a3) are present as salt groups at from 40 to 120%, preferably from 50 to 80%.

The acid numbers of the hydroxy-functional polyester-polyurethane dispersions according to the invention incorporated in component a3) are 5.0 to 14.5 mg KOH / g substance, preferably 8.0 to 11 mg KOH / g substance, in each case based on the aqueous dispersion of the polyester -Polyurethans.

The average molecular weight M _{w of} the polyester polyurethane dispersion A), determined, for example, by gel permeation chromatography using polystyrene as standard, is from 3,000 to 30,000 g / mol, preferably from 5,000 to 15,000 g / mol, more preferably from 6,000 to 10,000 g / mol and thus substantially lower than, for example, polyurethane dispersions according to the prior art.

The polyester a1) contained in the polyester polyurethane dispersion A) can be prepared by processes known per se with elimination of water at temperatures of 100 to 260 ° C, optionally with concomitant use of conventional esterification catalysts, preferably according to the principle of a melt or azeotropic condensation. Preferred production process for the polyester a1) is a melt condensation in vacuo or using an inert gas.

It is also possible to use mixtures of different polyesters and also mixtures of polyesters with different functionalities, the average functionality of the polyesters a1) being between 1.8 and 2.5, preferably 1.9 and 2.1, and particularly preferably 2.0 lies.

The polyesters a1) have computationally determined theoretical molecular weights of 500 to 3000 g / mol, preferably 500 to 1000 g / mol.

The theoretical molecular weight of the polyester is determined according to the formula: mass of the batch [g] / (mol COOH + mol OH) - Val COOH.

• a1_i) 30 bis 77 Gew.-%, bevorzugt 40 bis 60 Gew.-% mindestens einer, mindestens difunktionellen Carbonsäure bzw. deren Anhydrids,
• a1_ii) 23 bis 70 Gew.-%, bevorzugt 40 - 60 Gew.-% mindestens eines Diols,
• a1_iii) 0 bis 10 Gew.-% mindestens eines Alkohols mit mehr als 2 Hydroxylgruppen,
• a1_iv) 0 bis 10 Gew.-% sonstige hydroxy- und/oder carboxyfunktioneller Komponenten und/oder Caprolacton.

Preferably used polyesters a1) are reaction products of

• a1 _i ) from 30 to 77% by weight, preferably from 40 to 60% by weight, of at least one at least difunctional carboxylic acid or its anhydride,
• a1 _ii ) from 23 to 70% by weight, preferably from 40 to 60% by weight, of at least one diol,
• a1 _iii ) 0 to 10% by weight of at least one alcohol having more than 2 hydroxyl groups,
• a1 _iv ) 0 to 10% by weight of other hydroxy- and / or carboxy-functional components and / or caprolactone.

Suitable polyester raw materials a1 _i ) are, for example, phthalic anhydride, isophthalic acid, terephthalic acid, adipic acid, sebacic acid, suberic acid, succinic acid, maleic anhydride, fumaric acid, dimer fatty acids, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, cyclohexanedicarboxylic acid and / or trimellitic anhydride or mixtures thereof.

Preferred components a1 _i ) are adipic acid, phthalic anhydride, tetrahydrophthalic anhydride, isophthalic acid or glutaric acid, particularly preferred are adipic acid and hexahydrophthalic acid or phthalic acid and their anhydrides.

Suitable polyester raw materials a1 _ii ) are, for example, 1,2-ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1,2-propylene glycol, dipropylene glycol, tripropylene glycol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,6 Hexanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, 1,4-cyclohexanediol, butenediol, butynediol, hydrogenated bisphenols, trimethylpentanediol, 1,8-octanediol and / or tricyclodecanedimethanol and mixtures thereof.

Preferred components a1 _ii ) are 1,4-butanediol, neopentyl glycol, 1,2-propylene glycol, ethylene glycol, diethylene glycol or 1,6-hexanediol.

Preferred components a1 _ii ) are neopentyl glycol, butanediol and hexanediol.

Suitable polyester raw materials a1 _iii ) are, for example, trimethylolpropane, ethoxylated trimethylolpropane, propoxylated trimethylolpropane, propoxylated glycerol, ethoxylated glycerol, glycerol, pentaerythritol, castor oil and mixtures thereof.

Preferred component a1 _iii ) is trimethylolpropane.

Suitable optionally used polyester raw materials a1 _iv ) are, for example C ₈ -C ₂₂ -fatty acids such as 2-ethylhexanoic acid, stearic acid, hydrogenated fatty acids, benzoic acid, monofunctional alcohols such as butyl glycol, butyldiglycol, cyclohexanol, other monofunctional alcohols such as polyethylene oxides, polypropylene oxides, polyethylene / propylene oxide - or block copolymers and mixtures thereof.

The structural component a2) are linear, hydroxy-functional polycarbonates. Suitable polycarbonates a2) are those which are obtainable, for example, by reaction of carbonic acid derivatives, for example diphenyl carbonate, dimethyl carbonate or phosgene, with polyols, preferably diols. Examples of such diols are ethylene glycol, 1,2- and 1,3-propanediol, 1,3- and 1,4-butanediol, 1,6-hexanediol, 1,8-octanediol, neopentyl glycol, 1,4-bis-hydroxymethylcyclohexane, 2 Methyl-1,3-propanediol, 2,2,4-trimethylpentanediol-1,3, dipropylene glycol, polypropylene glycols, dibutylene glycol, polybutylene glycols, bisphenol A, tetrabromobisphenol A but also lactone-modified diols in question. Preferably, the diol component contains 40 to 100 wt .-% of hexanediol, preferably 1,6-hexanediol and / or hexanediol derivatives, preferably those which in addition to terminal OH groups ether or ester groups, for example products which by reaction of 1 mol Hexanediol with at least 1 mole, preferably 1 to 2 moles of caprolactone or by etherification of hexanediol with itself to di- or trihexylenglycol were obtained. Polyether-polycarbonate diols can also be used. The hydroxyl polycarbonates should be substantially linear. However, they may optionally be easily branched by the incorporation of polyfunctional components, especially low molecular weight polyols. For example, glycerol, trimethylolpropane, hexanetriol-1,2,6, butanetriol-1,2,4, trimethylolpropane, pentaerythritol, quinitol, mannitol, sorbitol, methyl glycoside or 1,3,4,6-dianhydrohexitols are suitable for this purpose. The preparation of the polycarbonate polyols is preferably carried out according to the in the EP-A 1 404 740 (Pp. 6-8, examples 1-6) and EP-A 1 477 508 (Page 5, Example 3) described manufacturing method.

Particularly preferred polycarbonate polyols a2) are those which contain at least 25% by weight of 1,4-butanediol as synthesis component and have an average hydroxyl functionality of from 1.6 to 4, preferably from 1.8 to 3 and particularly preferably from 1.9 to 2, 3 and a number average Molecular weight of 240 to 8000 g / mol, preferably from 500 to 3000 g / mol, particularly preferably from 750 to 2500 g / mol. The diol component preferably contains from 45 to 100% by weight of 1,4-butanediol, and from 1 to 55% by weight of 1,6-hexanediol, particularly preferably from 60 to 100% by weight of 1,4-butanediol and from 1 to 40% by weight .-% 1,6-hexanediol.

The hydroxylpolycarbonates are preferably linear, but may optionally be branched by the incorporation of polyfunctional components, in particular low molecular weight polyols. Particularly preferred components a2) are based on mixtures of 1,4-butanediol and 1,6-hexanediol and have an average hydroxyl functionality of 1.9 to 2.05.

Component a3) contains at least one ionic or potentially ionic compound having at least one acid group and at least one isocyanate-reactive group. Suitable acid groups are e.g. Carboxyl and sulphonic acid groups. Suitable isocyanate-reactive groups are e.g. Hydroxyl and / or amino groups.

Component a3) is preferably at least one, preferably one or two, hydroxyl-containing carboxylic acid. Dimethylolpropionic acid, dimethylolbutyric acid and / or hydroxypivalic acid are particularly preferred as component a3), very particular preference is given to using dimethylolpropionic acid.

Also suitable acids are, for example, other 2,2-bis (hydroxymethyl) alkanecarboxylic acid, such as dimethylolacetic acid or 2,2-dimethylolpentanoic acid, dihydroxysuccinic acid, Michael addition products of acrylic acid with amines such as isophoronediamine or hexamethylenediamine, or mixtures of such acids and / or dimethylolpropionic acid and / or hydroxypivalic acid. Likewise possible is the use of sulfonic acid diols optionally having ether groups US-A 4,108,814 or 2-aminoethyl-aminoethanesulphonic acid.

The free acid groups represent "potentially ionic" groups, while the salt-like groups, carboxylate or sulfonate groups obtained by neutralization with neutralizing agents are "ionic" groups.

Suitable polyisocyanates of component a4) are the aromatic, araliphatic, aliphatic or cycloaliphatic polyisocyanates known per se with an NCO functionality of preferably ≥ 2, which also include iminooxadiazinedione, isocyanurate, uretdione, urethane, allophanate, biuret, Urea, oxadiazinetrione, oxazolidinone, acylurea and / or may have carbodiimide structures. These can be used individually or in any mixtures with each other.

Examples of suitable polyisocyanates a4) are butylene diisocyanate, hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), 2,2,4- and / or 2,4,4-trimethylhexamethylene diisocyanate, the isomeric bis (4,4'-isocyanatocyclohexyl) methanes or mixtures thereof any isomer content, isocyanatomethyl-1,8-octane diisocyanate, 1,4-cyclohexylene diisocyanate, 1,4-phenylene diisocyanate, 2,4- and / or 2,6-toluene diisocyanate, 1,3- and 1,4-bis (2 isocyanato-prop-2-yl) -benzene (TMXDI), 1,3-bis (isocyanato-methyl) -benzene (XDI), 1,5-naphthylene-diisocyanate, 2,4'- or 4,4'-diphenylmethane-diisocyanate, triphenylmethane 4,4 ', 4 "-triisocyanate or derivatives based on the aforementioned diisocyanates with uretdione, isocyanurate, urethane, allophanate, biuret, iminooxadiazinedione and / or Oxadiazintrionstruktur with more than 2 NCO groups.

As an example of a non-modified polyisocyanate having more than 2 NCO groups per molecule, see e.g. 4-Isocyanatomethyl-1,8-octane diisocyanate (nonane triisocyanate) called.

Preference is given to polyisocyanates or polyisocyanate mixtures of the aforementioned type with exclusively aliphatic and / or cycloaliphatic bound isocyanate groups. Particularly preferred are hexamethylene diisocyanate, isophorone diisocyanate, the isomeric bis (4,4'-isocyanatocyclohexyl) methanes and mixtures thereof.

The process for the preparation of the aqueous polyester-polyurethane dispersion can be carried out in one or more stages in homogeneous or in multistage reaction, partly in disperse phase. After completely or partially carried out polyaddition from a1) to a4) takes place a dispersing, emulsifying or dissolving step. This is followed, if appropriate, by a further polyaddition or modification in disperse phase.

For the preparation of the aqueous polyester-polyurethane dispersions, all methods known from the prior art, such as e.g. Prepolymer mixing process, acetone process or melt dispersing process.

Suitable neutralizing agents which may already be present in the reaction of components a1) to a4) are e.g. Triethylamine, N-methylmorpholine, dimethylisopropylamine, ethyldiisopropylamine, dimethylcyclohexylamine, triethanolamine, dimethylethanolamine, ammonia, potassium hydroxide and / or sodium hydroxide.

The hydroxy-functional polyester-polyurethane dispersions A) generally contain from 0 to 10% by weight, preferably from 0 to 3% by weight, of organic solvents.

The optionally performed distillative removal of excess amounts of solvent may e.g. under reduced pressure at e.g. 20 to 80 ° C during or after dispersing in / with distilled water.

The solids content of the polyester polyurethane dispersion A) is 40 to 60 wt .-%, preferably 50 to 57 wt .-%.

The dispersions A) have particle diameters determined e.g. by LKS measurements, from 80 to 500 nm, preferably from 100 to 200 nm.

The hydroxy-functional, urethane-containing polyester dispersions A) are combined in combination with, optionally hydrophilized, polyisocyanates B) with free isocyanate groups to form the aqueous 2-component coating compositions according to the invention. In this use, the coating agent has a limited pot life of up to 24 hours. The coatings produced from it are curable at room temperature to 120 ° C.

As component B) polyisocyanates are used with free isocyanate groups. Suitable polyisocyanates are, for example, based on isophorone diisocyanate, hexamethylene diisocyanate, 1,4-diisocyanatocyclohexane, bis (4-isocyanatocyclohexane) methane or 1,3-diisocyanatobenzene or polyisocyanates based on lacquer polyisocyanates such as allophanate, uretdione, biuret or isocyanurate groups lacquer polyisocyanates containing 1,6-diisocyanatohexane, isophorone diisocyanate or bis (4-isocyanatocyclohexane) methane or urethane groups and based on 2,4- and / or 2,6-diisocyanatotoluene or isophorone diisocyanate, on the one hand, and low molecular weight polyhydroxyl compounds, such as trimethylolpropane, the isomers Propanediols or butanediols or any mixtures of such polyhydroxyl compounds on the other hand.

Preferred as components B) are low-viscosity, hydrophobic or hydrophilicized polyisocyanates with free isocyanate groups based on aliphatic, cycloaliphatic, araliphatic and / or aromatic isocyanates, particular preference being given to aliphatic or cycloaliphatic isocyanates. These polyisocyanates generally have a viscosity of from 10 to 3500 mPas at 23 ° C. If necessary, the polyisocyanates may be used in admixture with small amounts of inert solvents to lower the viscosity to a value within the stated range. Also Triisocyanatononan can be used alone or in mixtures as a crosslinking component. Water-soluble or dispersible polyisocyanates are obtainable, for example, by modification with carboxylate, sulfonate and / or polyethylene oxide groups and / or polyethylene oxide / polypropylene oxide groups.

For the hydrophilization of the polyisocyanates B), it is preferable to react the polyisocyanates with substoichiometric amounts of monohydric, hydrophilic polyether alcohols. The preparation of such hydrophilicized polyisocyanates is for example in the EP-A 0 540 985 described. Also preferred are those in the EP-A 0 959 087 described allophanate-containing polyisocyanates prepared by reacting low-monomer polyisocyanates with Polyethylenoxidpolyetheralkoholen under allophanatization. Also in the DE-A 100 078 21 described water-dispersible polyisocyanate mixtures based on Triisocyanatononan are suitable, and with ionic groups (sulfonate, phosphonate) hydrophilized polyisocyanates, such as those in the DE-A 100 24 624 are described. Likewise possible is the hydrophilization by addition of commercially available emulsifiers.

Particular preference is given to using as component B) those mixtures which contain flexibilized polyisocyanate components B) which are readily obtained by prepolymerization of the abovementioned polyisocyanate components with preferably di- to trifunctional polyol components, particularly preferably polyol components as already mentioned under structural components a1).

Other preferred hardener components are polyisocyanates modified with sulfonate groups, as described, for example, in US Pat DE-A 100 24 624 be described, are used.

Of course, it is also possible to use component B) as so-called blocked polyisocyanates. The blocking of the above-mentioned polyisocyanates with free isocyanate groups takes place according to the known prior art by reaction of the polyisocyanates with free isocyanate groups with suitable blocking agents. Suitable blocking agents for these polyisocyanates are, for example, monohydric alcohols, such as methanol, ethanol, butanol, hexanol, cyclohexanol, benzyl alcohol, oximes, such as acetoxime, methyl ethyl ketoxime, cyclohexanone oxime, lactams, such as ε-caprolactam, phenols, amines, such as diisopropylamine or dibutylamine, dimethylpyrazole or triazole, and dimethyl malonate. Diethyl malonate or dibutyl malonate.

If the dispersions A) are applied alone to substrates, preferably films, then clear, very well-running layers without defects or craters are obtained and very high layer thicknesses of more than 100 μm are possible. The dispersions A) show no pronounced physical drying, that is, the layers remain more or less sticky or grippy. Cured, tack-free and hard layers are obtained only by combination with at least one crosslinker polyisocyanate B) and curing.

The aqueous 2K polyurethane paint according to the invention applied as a coating on top of the carrier films may, in addition to the components A) and B), optionally contain the customary auxiliaries and additives C), such as organic and / or inorganic pigments or metallic pigments based on Aluminum flakes, fillers such as carbon black, silica, talc, kaolin, glass powder or in the form of fibers and mixtures of these and / or other common materials for the production of paints, coatings and adhesives.

To achieve particular effects, it is also possible to add small amounts of auxiliaries customary in the paint and adhesives industry in the preparation of the polyester dispersion A), such as, for example, surface-active substances, emulsifiers, stabilizers, anti-settling agents, UV stabilizers, catalysts for the crosslinking reaction, defoamers, antioxidants, anti-skinning agents, leveling agents, thickeners and / or bactericides.

In a preferred embodiment, the aqueous two-component polyurethane coating according to the invention contains a silicone-containing silicone additive, with which a particularly smooth surface is obtained.

The two-component polyurethane lacquer according to the invention is basically suitable for the coating, lacquering, bonding, treatment and sealing of a wide variety of substrates, in particular metals, wood, ceramics, stone, concrete, bitumen, hardboard, glass, porcelain, plastics, leather and / or textiles Kind suitable. A preferred application is the coating of plastic. Particularly preferred is the coating of polycarbonate.

The aqueous two-component polyurethane lacquers according to the invention can be applied to the substrate to be coated by methods known per se, such as spraying, flooding, casting, dipping, rolling, brushing.

The aqueous two-component polyurethane coatings can also be used as part of a multi-layer coating structure, consisting for example of primer and / or filler and / or basecoat and / or topcoat. Wet-in-wet coating processes are also possible in which at least two layers are applied one after the other, if necessary pre-dried and then baked together. The paints may also contain proportionately one or more other aqueous dispersions, for example based on polyester, polyurethane, polyurethane-polyacrylate, polyacrylate, polyether, polyester-polyacrylate, alkyd resin, polymer, polyamide / imide or polyepoxide

The aqueous two-component polyurethane lacquers according to the invention used as a coating for the production of the carrier film are characterized by a very good processability. The resulting coatings have excellent film appearance and flow, very low crater susceptibility, good resistance properties, a balanced hardness / elasticity level and a very good storage stability. The carrier films also exhibit excellent blocking resistance, i. The carrier films can be unrolled easily after rolling up from the roll again.

To coat portions of the film, e.g. Screen printing preferred. The layer thicknesses can be between 2 microns and 100 microns, preferably between 5 and 75 microns, more preferably between 5 and 50 microns.

For the production of the carrier films, conventional plastic films, e.g. from PET, polycarbonate, PMMA, polysulfone, etc. are used. Optionally, the films may be pretreated by methods such as corona treatment, etc. The carrier films preferably have thicknesses between 2 and 2,000 micrometers. Preferably, carrier films of polycarbonate and polycarbonate blends are used. The carrier films may also be so-called composite films made of a plurality of plastic layers.

Suitable carrier films are in principle all known per se or commercially available polycarbonates. The polycarbonates suitable as a carrier film preferably have a molecular weight in the range from 10,000 to 60,000 g / mol. They are eg according to the procedures of DE-B-1 300 266 by interfacial polycondensation or according to the method of DE-A-1 495 730 by reaction of diphenyl carbonate with bisphenols available. Preferred bisphenol is 2,2-di (4-hydroxyphenyl) propane, generally - as hereinafter referred to as bisphenol A.

Instead of bisphenol A, it is also possible to use other aromatic dihydroxy compounds, in particular 2,2-di (4-hydroxyphenyl) pentane, 1,6-dihydroxynaphthalene, 4,4'-dihydroxydiphenylsulfane, 4,4'-dihydroxydiphenyl ether, 4,4'-dihydroxynaphthalene. Dihydroxydiphenylsulfone, 4,4'-dihydroxydiphenylmethane, 1,1-di (4-hydroxyphenyl) ethane, 4,4'-dihydroxydiphenyl- or Dihydroxydiphenylcycloalkane, preferably Dihydroxydiphenylcyclohexane or Dihydroxycyclopentane and mixtures of the aforementioned dihydroxy compounds.

Polycarbonates which are particularly suitable as carrier film are those which contain units which are derived from resorcinol or alkyl resorcinol esters, as described, for example, in US Pat WO 00/15718 or WO 00/26274 to be discribed; These polycarbonates are marketed, for example, General Electric Company under the trademark Sollx ^®.

In addition to these carrier films and blends or mixtures of plastics can be used. Blends of polycarbonate and polyesters, for example polybutylene terephthalate or polyethylene terephthalate, and polyesters of cyclohexanedicarboxylic acid and cyclohexanedimethanol have proven particularly advantageous. Such products are sold under the names Bayfol ^® from Bayer MaterialScience AG or Xylex ^® by General Electric Company.

Copolycarbonates according to the US-A 3,737,409 be used; Of particular interest are copolycarbonates based on bisphenol A and di- (3,5-dimethyldihydroxyphenyl) sulfone, which are characterized by a high heat resistance. It is also possible to use mixtures of different polycarbonates.

Impact-resistant PMMA is a polymethyl methacrylate which is impact-modified by suitable additives and is preferably used. Suitable impact-modified PMMA are described, for example by M. Stickler, T.Rhein in Ullmann's Encyclopedia of Industrial Chemistry Vol. A 21, pp. 473-486, VCH Publishers Weinheim, 1992 , and H. Domininghaus, The plastics and their properties, VDI-Verlag Dusseldorf, 1992 ,

For the production of the carrier film, all known methods, for example by adapter or coextrusion or stacking of layers in question. In addition, the carrier film can also be cast from solution.

The surface of the carrier film can be glossy, structured or matted.

As Hinterspritz-, Hintergieß- or Hinterpresskunststoffe all known thermoplastic polymeric materials come into question. Suitable are e.g. thermoplastic polymers such as polyolefins, e.g. Polyethylene or polypropylene, polyester, e.g. Polybutylene terephthalate (PBT) and polyethylene terephthalate (PET), polycycloolefins, poly (meth) acrylates, polyamides, polycarbonates, polyurethanes, polyacetals, e.g. Polyoxymethylene (POM), polystyrenes, polyphenylene ethers, polysulfones, polyethersulfones, polyether ketones, styrene (co) polymers or mixtures of the aforementioned polymers.

Particularly suitable polycarbonates are bisphenol A and TMC bisphenol polycarbonates. Preferred polymer blends include polycarbonate and polybutylene terephthalate or polycarbonate and ABS polymer.

Due to the very good deformation properties and the good adhesion and the good stretching behavior of the coating in the carrier film can not only flat, ie substantially flat, or shell-shaped moldings, but also those with indentations and formations, and vertical formations or depressions, such as mobile phone keyboards, getting produced. The good surface properties associated with the carrier films are therefore also accessible in the case of composite moldings with sophisticated geometry.

The carrier films of the invention are used in telecommunications equipment, in vehicle, ship and aircraft.

The present invention also relates to the use of the carrier film according to the invention for the equipment of plastic moldings, preferably screen housings.

The invention will be explained in more detail with reference to the following examples.

Examples

Unless otherwise indicated, all percentages are by weight.

Substances used and abbreviations:

BYK ^® 348: Wetting agent (BYK-Chemie, Wesel, DE) BYK ^® 337: Surface additive (BYK-Chemie, Wesel, DE) MPA: 1-methoxy-2-propyl Tinuvin ^® 292 HALS amine (Ciba GmbH, Lampertheim, DE) Tinuvin ^® 384-2 UV absorber (Ciba GmbH, Lampertheim, DE) Bayhydur ^® VPLS 2306 Elasticated, hydrophilic polyisocyanate, (Bayer Material Science AG, DE); average functionality 2.5. Bayhydur ^® XP 2655 Hydrophilic polyisocyanate, (Bayer Material Science AG, DE); average functionality 3.1.

The solids contents were determined according to DIN-EN ISO 3251.

NCO contents were determined volumetrically in accordance with DIN-EN ISO 11909, unless expressly stated otherwise.

Example 1 Polyesterpolyol

In a 151-reaction vessel with stirrer, heater and water with a condenser, 1281 g of phthalic anhydride, 5058 g of adipic acid, 6387 g of 1,6-hexanediol and 675 g of neopentyl glycol were weighed and heated to 140 ° C under nitrogen in one hour. In a further 9 hours was heated to 220 ° C and condensed at this temperature until an acid number less than 3 was reached. The polyesterpolyol thus obtained had a viscosity (determined as the flow time of an 80% strength solution of the polyester in methoxypropyl acetate in the DIN 4 cup at 23 ° C.) of 54 seconds and an OH number of 160 mg KOH / g.

Example 2 Preparation of a polycarbonate diol based on 1,4-butanediol and 1,6-hexanediol

1,223 g of 1,4-butanediol and 535 g of 1,6-hexanediol were placed in a flask and heated to 100 ° C. Finally, about 2 1 / h nitrogen were introduced into the diol and 20 mbar vacuum applied and the mixture as long dehydrated (about 2 hours) until the water content was ≤ 0.1%.

Thereafter, 0.44 g of ytterbium (III) acetylacetonate were added, the diol mixture was heated to 110 ° C. Then 2297 g of dimethyl carbonate were run in about 20 minutes and kept the reaction mixture under reflux for 24 h. Finally, the temperature was raised to 150 ° C and any distillate was removed. This was followed by a further increase to 180 ° C followed by another distillation phase.

The reaction mixture was cooled to 130 ° C and the pressure was lowered to 10 mbar. This was followed by an increase in the oil bath temperature from 130 ° C to 180 ° C within 2 h, the distillation head temperature did not exceed 60 ° C. After reaching 180 ° C, this temperature was maintained for 6 h.

Subsequently, the reaction mixture was cooled to 130 ° C and the pressure was lowered to 10 mbar. This was followed by an increase in the oil bath temperature from 130 ° C to 180 ° C within 2 h, the distillation head temperature did not exceed 60 ° C. After reaching 180 ° C, this temperature was maintained for 6 h. The reaction mixture was cooled to room temperature and the characteristics of the product determined.

A polycarbonate diol having a hydroxyl number of 57.3 mg KOH / g and a viscosity of 115 Pas at 23 ° C. is obtained.

Example 3 Preparation of a polyearbonate diol based on 1,4-butanediol and 1,6-hexanediol

1239 g of 1,4-butanediol and 542 g of 1,6-hexanediol were placed in a flask and heated to 100 ° C in an oil bath. Finally, about 2 1 / h nitrogen were introduced into the diol and 20 mbar Vakkum applied and the mixture as long dehydrated (about 2 hours) until the water content was ≤ 0.1%.

Thereafter, 0.44 g of ytterbium (III) acetylacetonate added, the diol mixture was heated to 110 ° C. Then 2180 g of dimethyl carbonate were allowed to run in about 20 minutes and the reaction mixture was refluxed for 24 h. Finally, the temperature was raised to 150 ° C and any distillate was removed. This was followed by a further increase to 180 ° C followed by another distillation phase.

The reaction mixture was cooled to 130 ° C and the pressure was lowered to 10 mbar. This was followed by an increase in the oil bath temperature from 130 ° C to 180 ° C within 2 h, the distillation head temperature did not exceed 60 ° C. After reaching 180 ° C, this temperature was maintained for 6 h.

Subsequently, the reaction mixture was cooled to 130 ° C and the pressure was lowered to 10 mbar. This was followed by an increase in the oil bath temperature from 130 ° C to 180 ° C within 2 h, the distillation head temperature did not exceed 60 ° C. After reaching 180 ° C, this temperature was maintained for 6 h. Thereafter, the reaction mixture was cooled to room temperature and the characteristics of the product determined.

There is obtained a polycarbonate diol having a hydroxyl number of 113.4 mg KOH / g and a viscosity of 13600 mPas at 23 ° C.

Example 4 Hydroxy-functional PUR dispersion

In a 61 reaction vessel with cooling, heating and stirring device 1170 g of the polyester polyol from Example 1 were initially charged in a nitrogen atmosphere and together with 1140 g of polycarbonate diol from Example 2, 90 g of trimethylolpropane, 120 g of dimethylolpropionic acid and 3.8 g of tin ( II) -octoate heated to 130 ° C and homogenized for 30 min. The mixture was then cooled to 80 ° C, 480 g of hexamethylene diisocyanate added with vigorous stirring, heated to 140 ° C using the exotherm and the mixture kept at this temperature until no more NCO groups could be determined.

Subsequently, the polyurethane thus obtained was cooled to 90 ° -100 ° C, 47 g of dimethylethanolamine (degree of neutralization 60%) was added, homogenized for 15 minutes and dispersed with 2270 g of demineralized water. The resulting aqueous polyurethane resin dispersion had an OH content (100%) of 1.4%, an acid number (100%) of 16.8, an average particle size of 110 nm and a viscosity of about 2020 mPas ( 23 ° C, D = 40 s ^-1 ) at a solids content of 51.2 wt .-%.

Example 5 Hydroxy-functional PUR dispersion

In a 61-reaction vessel with cooling, heating and stirring 1170 g of the polyester polyol from Example 1 were initially charged and together with 1140 g of polycarbonate diol from Example 3, 90 g of trimethylolpropane, 120 g of dimethylolpropionic acid, 125 g of N-methylpyrrolidone and 3 , 8 g of tin (II) octoate heated to 130 ° C and homogenized for 30 min. The mixture was then cooled to 80 ° C, 480 g of hexamethylene diisocyanate added with vigorous stirring, heated to 140 ° C using the exotherm and the mixture kept at this temperature until no more NCO groups could be determined.

Subsequently, the polyurethane thus obtained was cooled to 90 ° -100 ° C, 39 g dimethylethanolamine (degree of neutralization 50%) was added, homogenized for 15 minutes with 2270th dispersed demineralized water. The aqueous polyurethane resin dispersion thus obtained had an OH content (100%) of 1.4%, an acid number (100%) of 16.3, an average particle size of 150 nm and a viscosity of about 1680 mPas ( 23 ° C, D = 40 s ^-1 ) at a solids content of 55.9 wt .-%.

Example 6 Scratch-Resistant Clearcoat (Comparative Example) Preparation of the base varnish (component A)

To 56.80 g of the polyurethane dispersion from Example 5 were added 0.45 g of Byk® 347, 0.77 g of Byk® 337 and 22.17 g of distilled water and stirred thoroughly.

Preparation of the hardener solution (component B)

To 8.60 g Bayhydur XP ^® 2655 0.77 g Tinuvin ^® 292 (50% solution in MPA), 1.16 g Tinuvin ^® were added 384-2 (50% solution in MPA), and 9.28 g MPA and intimately mixed.

Example 7 Scratch-resistant clearcoat Preparation of the base varnish (component A)

To 51.59 g of the polyurethane dispersion from Example 5 were added 0.45 g of ^Byk® 347, 0.77 g of ^Byk® 337 and 24.59 g of distilled water and stirred thoroughly.

Preparation of the hardener solution (component B)

To 11.34 g of a mixture of Bayhydur XP ^® 2655 / Bayhydur ^® VP LS 2306 (50 wt .-%), 0.77 g Tinuvin ^® were 292 (50% solution in MPA), 1.16 g Tinuvin ^® Add 384-2 (50% solution in) and 9.33 g of 1-methoxypropyl acetate (MPA) and stir thoroughly.

Example 8 (comparison)

Unpainted polycarbonate film (film thickness: 175 μm)

Mixing of the base coat with the hardener and application

The above-listed components A (stock paint) and B (hardener) were respectively mixed together and intimately stirred (Dispermat, 2 minutes at 1000 rpm). The mixtures were then knife-coated onto polycarbonate film (175 μm), flashed off at room temperature for 5 minutes and then 45 minutes. dried at 80 ° C in a convection oven. High-gloss films having a dry film thickness of about 15 μm were obtained. An overview of the determined coating properties of the films is shown in the table.

Paint technical properties:

Table 1: example 6 7 8th (Comparison) (Inventive invention) (unpainted PC film, comparison) liability gt0 gt0 - scratch resistance 1 0 5 chemical resistance isopropanol 0 0 0 rapeseed oil 0 0 3 Nivea - Hand Cream 0 0 0

Test methods:

Liability: According to DIN EN ISO 2409

Scratch resistance:

• 0 : keine Kratzer erkennbar
• 1 : vereinzelt Kratzer erkennbar
• 2 : Kratzer erkennbar
• 3 : deutliche Kratzer erkennbar
• 4 : viele Kratzer erkennbar
• 5 : sehr viele Kratzer erkennbar

The scratch resistance was performed with a Crockmeter Atlas CM6. The film surface was scratched with a polishing paper (9 μm, 10 or 40 double strokes). The assessment of the scratched film surface according to DIN 53230:

• 0: no scratches recognizable
• 1: occasional scratches visible
• 2: Scratches recognizable
• 3: visible scratches
• 4: many scratches recognizable
• 5: very many scratches recognizable

Chemical resistance:

Test with isopropanol, rapeseed oil, Nivea hand cream.

Load duration 24 h at room temperature. The assessment of the loaded film surface is carried out according to DIN 53230.

DIN 53230 gives a relative rating scale for visual matching: <u> Table 2: </ u> identification number importance Explanations 0 not changed 1 Track changed - Swelling ring is very weak, recognizable only by mirrors in the light - Swelling ring is clearly interrupted 2 slightly changed - Swelling ring is visible in the light - Scratch marks recognizable 3 medium changed - closed swelling ring is clearly visible - slightly scratchable 4 changed a lot - Closed swelling ring is very pronounced - scratchable 5 changed very much - scratchable

Deep drawing capability by means of high pressure deformation

The coated according to Examples 6 and 7 Makrofol DE 1-1 ^® films (Bayer Material Science AG, DE) were prepared according to DE-A 3840542 deformed. The experiments were carried out on a high-pressure forming system of HDVF Kunststoffmaschinen GmbH, type SAMK 360. As a deformation tool, a Handyschalenwerkzeug was used. The deformation parameters were selected as follows: heating rate: 14 sec, heating field setting 240 ° C - 280 ° C, mold temperature 80 ° C, deformation pressure 80 bar. The deformed films were visually evaluated for adhesion, cracking and coating after deformation.

Test results of the coated with the coating materials 6 and 7 ^® Makrofol DE 1-1 films.

Table 3: example Crack formation at 14 sec heating rate (tool: mobile phone shell) 6 Cracking edge 7 flawless

The results listed show that only with the paints formulated according to the invention can very good thermoformability of the coated film be obtained.

Claims (9)

Containing aqueous 2-component polyurethane paint A) at least one hydroxy-functional polyester polyurethane dispersion containing as structural components a1) linear or branched, hydroxy-functional polyesters, a2) linear, hydroxy-functional polycarbonates, a3) at least one ionic or potentially ionic compound having at least one acid group and at least one isocyanate-reactive group, a4) at least one (cyclo) aliphatic diisocyanate and a5) low molecular weight hydroxy and / or amino functional compounds.
such as B) at least one polyisocyanate crosslinker, characterized in that the crosslinking ratio of isocyanate groups from B) and hydroxy groups from A) is between 1.0: 1 and 1.6: 1. Aqueous two-component polyurethane paint according to claim 1, characterized in that the crosslinking ratio of isocyanate groups from B) and hydroxy groups from A) is between 1.2: 1 and 1.4: 1. Aqueous two-component polyurethane paint according to claim 1, characterized in that the average functionality of the polyisocyanates B) is 2.5 to 3.3. Aqueous two-component polyurethane paint according to claim 1, characterized in that the polyester polyurethane dispersion A) 20 to 50 wt .-% of component a1), 20 to 50 wt .-% of component a2), 2 to 6 wt .-% component a3), 10 to 30 wt .-% of component a4), 0.5 to 10 wt .-% component a5), wherein the percentages a1) to a5) to 100 wt .-% complement. Aqueous two-component polyurethane paint according to claim 1, characterized in that the acid numbers incorporated in component a3) are hydroxy-functional Polyester polyurethane dispersion A) at 5.0 to 14.5 mg KOH / g of substance, based in each case on the aqueous dispersion of the polyester-polyurethane, are. Aqueous two-component polyurethane paint according to claim 1, characterized in that the average molecular weight M _{w of} the polyester polyurethane dispersion A), determined by gel permeation chromatography with polystyrene as standard, is 5,000 to 15,000 g / mol. Aqueous 2K polyurethane paint according to claim 1, characterized in that polyester a1) reaction products of a1 _i ) from 30 to 77% by weight of at least one at least difunctional carboxylic acid or its anhydride, a1 _ii ) from 23 to 70% by weight of at least one diol, a1 _iii ) 0 to 10% by weight of at least one alcohol having more than 2 hydroxyl groups, a1 _iv ) 0 to 10 wt .-% of other hydroxy and / or carboxy-functional components and / or caprolactone. Aqueous two-component polyurethane paint according to claim 1, characterized in that polycarbonate polyols a2) are those which contain at least 25 wt .-% of 1,4-butanediol as a synthesis component and an average hydroxyl functionality of 1.6 to 4 and a number average molecular weight of 240 to 8000 g / mol. Use of the aqueous 2K polyurethane paint according to claim 1 for the production of coated carrier films.